Heretofore, as shown in the following formulas (1) and (2), a catalyst used for denitration by reduction of a nitrogen oxide in the presence of ammonia has been developed. For example, a catalyst containing tungsten oxide, zirconia, and a metal, such as a rare earth metal, as an active ingredient (Japanese Patent Application Laid-open Publication No. 2005-238196; PCT International Application Publication WO 05/082494) and a catalyst containing zirconia, tungsten oxide, and cerium oxide (Japanese Patent Application Laid-open Publication No. Hei2-56250) have been disclosed.NO2+2NH3+1/2O2→3/2N2+3H2O  Formula (1)NO+NH3+1/4O2→N2+3/2H2O  Formula (2)